This invention relates to a system wherein water evaporated from salt water is used as a source of fresh water for either agriculture and/or aquaculture.
Successful wide scale agriculture in arid lands which are adjacent to unlimited supplies of sea water have always presented a perplexing problem, namely the inability to use sea water for plant growth.
Where sea water is used, it is typically desalinized such as by evaporation, osmosis or other separation techniques. This separation step adds considerably to the cost of the ultimate production of the crops.
A further drawback is one that has been discussed in my prior patents. When plants are placed in the soil, water and nutrients are not fully utilized because of the permeability of the soil. Thus if water sufficiently pure for crops is generated from sea water and used to irrigate crops in the ground, most of the water is wasted.
The aforementioned problems were overcome to a considerable degree by the invention disclosed in my prior U.S. Pat. No. 4,178,715. In that invention a plurality of channels were formed having a floor. The floor was spaced apart from a base and saline water flowed into a zone defined by the floor and the base. Temperature differences effected evaporation of pure water from the saline water. The evaporated water condensed and coalesced on the underside of the floor and permeated into the soil which the floor supported.
The present invention is directed to a system which is an improvement of the basic concepts disclosed in my aforementioned patent. Further, it is believed that the prior art is still best represented by the references cited in the aforementioned patent.
The present invention, relates to an apparatus and method for recovering a pure liquid vapor component from a contaminated liquid, which liquid the liquid vapor is in equilibrium with. This includes organic and inorganic wastes and aqueous wastes. More particularly the invention is directed to using water which would normally be considered contaminated for its intended use. More particularly, an apparatus and method are disclosed wherein the liquid vapor phase in equilibrium with the saline water is used to maintain the soil in which a plant is growing in a wetted condition without the saline water contacting the soil.
My invention comprises a structure and method to enhance the distribution of the liquid vapor and subsequent collection of the condensate. Additionally, the invention comprises controlling the levels of salinity of the water where it can range anywhere from brackish water to potable water and additionally the recovered water may be used for aquaculture as well as agriculture.
My invention includes flowing relatively contaminated water at a first higher temperature T.sub.1 into a zone which zone is at a second lower temperature T.sub.2, the liquid vapor in equilibrium with the water at temperature T.sub.2 being non-contaminated; flowing the liquid vapor from the zone into a soil bed, maintaining the liquid vapor in the soil bed and subsequently condensing the liquid vapor.
The basis for the use of the normally polluted water, such as sea water, for purposes of my invention, is that in tropical areas the typical ambient temperature during the day may range from 120.degree. to 130.degree. F., and the surface temperature of the water from 140.degree. to 160.degree. F. As is well understood there always exists a relationship among temperature, both dry and wet bulb, dew point, moisture content per pound of dry air, etc. If a given volume of air is cooled, its ability to hold moisture is diminished and condensation of the moisture from the air results if the temperature reduction of the air occurs within a defined space or on an exposed surface. These relationships can be determined from any psychrometric chart.
In my invention water and the air in which it is in equilibrium with is caused to pass and circulate under the floor of a soilbed. In the preferred embodiment of my invention diffuser tubes extend from a zone, defined by the upper surface of the water and the under surface of a soilbed, and into the soilbed. The sea water with the liquid vapor in equilibrium therewith, flows under and is in communication with the soilbed via the diffuser tubes during the day. The diffuser tubes allow the air containing the liquid vapor to permeate the entire soilbed. At the top surface of the soilbed the liquid vapor will essentially evaporate into the ambient. At the interface between the diffuser tubes and the soilbed and the floor of the soilbed, the liquid vapor content will essentially be the same as the liquid vapor content in equilibrium with the sea water in the zone. To maximize the amount of liquid vapor in the soilbed, i.e. prevent surface evaporation different colors of granules and sizes may be used to minimize the surface temperature.
Typically, in desert-like regions, the ambient temperature during the day may be 120.degree.-130.degree. F., and, as is well known, within a short period of time, i.e. an hour or so, the temperature may drop to 40.degree.-60.degree. F. at night. In that the sandbed becomes impregnated with the air carrying liquid vapor over a long period of time during the day, when the sudden drop in temperature occurs, the liquid vapor does not escape into ambient air. Rather the liquid vapor is entrapped by the soilbed (including surfaces of the floor, walls and diffusor tubes). The particles of the soilbed and inner walls form contact or heat exchange surfaces. When the temperature drops rapidly the liquid vapor condenses, thereby saturating the soilbed.